A percussive rock drilling machine comprises basically a cylinder in which a piston reciprocates. The blows of the piston transmit impact energy via a drill steel, the free end of which is a drill bit. The drill steel comprises a shank adapter, one or a plurality of drill rods and a drill bit, all of which comprises coupling joints. In a rock drilling machine, the whole drill steel when mounted comprises a continuous central longitudinal channel for flushing medium. The shank adapter is arranged extending in a central channel of the rock drilling machine.
The front end of the drill steel comprises a drill bit arranged to drill into the rock as it rotates. The rear end of the drill steel is connected to a drive unit via the shank adapter. The shank adapter is usually supported in the rock drilling machine by a front guide and a rear guide arranged at a distance from each other.
A drilling machine normally comprises two main parts, a front part and a rear part. In many drilling machines of today, the shank adapter is mounted such that a front guide is arranged in the front part supporting the shank adapter and a rear guide is arranged in a gear in the rear part having a driving function on the shank adapter.
When drilling holes in rock, the rock particles broken off by the blows must be continuously removed from the hole. To make rock drilling possible, these rock particles have to be transported away from the drill hole continuously. This is achieved by a flushing agent—air and/or water—passing through suitable passages in the drill bit. The cuttings—rock particles mixed with flushing medium—are generally carried away in the space between the rod and the wall of the hole.
The shank adapter is designed as a cylinder with an internal channel extending axially. In a rock drilling machine comprising a shank adapter, the flushing medium is applied into the flushing head and further via the shank adapter to the drill bit via the adapter channel and the tubular drill string.
To prevent the flushing medium from entering the drilling machine, the shank adapter is sealed against the flushing head by means of flushing seals. In this way, the flushing medium is prevented from entering the drill machine, which prevents damage to the drill machine.
In mine environments with damp air and occasionally saline flush water, the flushing water causes problem. The surface of the shank adapter quickly becomes corroded and the surface upon which the flushing seals must glide becomes highly wearing. The relatively short lifetime of the flushing seals is one important reason why rock drilling machines need to be serviced.
The document DE 4317037 A1 teaches a rock drilling machine comprising a flushing head, which is arranged in front of the drilling machine. In this design, the flush sealing is relatively unprotected against drill cuttings and its lifetime is shortened. Further, the shank adapter front guide is placed relatively close to the corresponding rear guide. This renders the guiding of the shank adapter less stable.
In prior art rock drilling machines, there is an alternative solution where the flushing head is arranged inside the front part of the drilling machine. When this kind of rock drilling machine needs to be serviced, the whole front part together with the shank adapter is demounted. Then, the shank adapter, the flushing head with flushing seals and a stop ring have to be detached from the front part and the flushing seals in the flushing head are exchanged.
After service, the parts have to be mounted again. Then, usually, there is a pin to be inserted in the flushing head to keep it in place and avoid rotational movements as well as providing a channel for delivering flushing water. Due to this pin, there is only one correct position for the flushing head and this position is hard to find.
This part of service is very heavy work and it takes a lot of effort and time to demount and mount the machine parts mentioned.
Thus, there are needs to reduce the service costs. These needs cannot be fulfilled by the rock drilling machines according to the above-mentioned prior art.